This week’s Hammer of Math looks at [TORRENT] weapons and explores their break-even points with weapons which must roll to hit and wound.
The traditional Hit, Wound, Save progression of Warhammer 40k results in an easily understood probability curve. The probability of a target hitting and wounding is the product of the probabilities of the two rolls succeeding. At best a 2+ to hit and 2+ to wound produce a 69.4% chance of success. This means that, barring the presence of re-rolls, roughly 1 out of every 3 attacks will fail to force the enemy to make a Save roll.
The [TORRENT] keyword completely upends this: With [TORRENT] weapons, an entire gatekeeping step in the form of the Hit roll is eliminated. This is a deceptively powerful effect, and changes the math significantly. So it’s worth exploring those situations where we can choose between a torrent weapon and once which must roll to hit, but has a higher strength characteristic or better AP.
The equivalency of a [TORRENT] weapon can be determined by taking the probability of the Wound roll and comparing it to the cumulative probability of a Hit and Wound roll for a given weapon using a BS. For example, a [TORRENT] weapon with a 5+ to wound will wound 33% of the time. That’s the same probability as weapon with a 3+ BS and a Wound roll target of 4+, meaning they’re equivalent. For another example, that same [TORRENT] weapon has a probability of Wounding that is 1.33 times that of a 4+ BS weapon with a Wound roll target of 4+. This means that latter profile needs 1.33 times more attacks to be equivalent to the [TORRENT] weapon.
It should also be noted that, given the prevalence of cover in 10th Edition 40k, the [IGNORE COVER] ability commonly featured with [TORRENT] weapons is often equivalent to a bonus point of Armour Penetration.
The chart below shows the equivalency for all of the different combinations. Start by selecting the Wound roll target for the [TORRENT] weapon, and then look at the Wound Target and BS to determine the equivalent number of attacks.
When looking at the chart we see some interesting results.
- The D6+3 shots from the Land Raider Redeemer flamestorm cannon is fantastic against a wide swath of targets faced by opponents, hitting a 4+ to Wound against T6 or lesser targets. This makes the probability of success higher than other weapons such as plasma guns which would get a 3+ to wound. A S8 weapon against a T4 target with a BS of 3+ needs 20% more attacks to be equivalent to the Flamestorm Cannon.
- When attacking a T12 target in cover and taking into account wounds and damage, the 3D6 (average 10.5 hits) S7 D3 hits from a Warhound inferno gun averages more wounds than the output of a supercharged plasma blastgun and is a little over 67% as effective as a turbo-laser destructor.
- The [TWIN-LINKED] bonus from Aggressor flamestorm gauntlets means that they Wound anything roughly 30% of the time, which is pretty close to a 5+ to wound. That puts the 4.5 hit they average at an advantage over weapons with fewer attacks, particularly when facing threats with invulnerable saves that disregard most AP.
The bottom line is that in situations where you can offset the traditional limitations with AP and short range, [TORRENT] is a surprisingly powerful ability. The advantage is enhanced when utilizing weapons which hit harder, with the flamestorm cannons being a very good example.
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